While not every class or interface is properly documented and annotated yet,
adding them to the docs should still be valuable.
Additionally it is a good reminder for ourselves to add some proper description
because things like missing a annotated class description really stand out
currently.
* Preliminary documentation of CallsCall and CallsMessageSource
* Documentation and cleaning up of CallsCallData
* Add data files and meson rules to create gtk-doc documentation
* Move some macros from util.h to calls-message-source.h